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Author Topic: Partial motors - what is the correct weight?  (Read 638 times)
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spr
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« on: March 04, 2018, 03:04:43 PM »

A semi-academic question:  The theory says that partial motors should be say 1/2 or 1/3 of the 1/1 motor weight. Is it so also in real life? Do you get 1/2 flight times and 1/2 elevation with exactly 1/2 weighing motors?  OR should we have a bit more rubber in partial motors to accomplish the knot weight?

The knot weights as much in full motor than in a 1/3 motor, which means that the loop length in 1/3 motor is less that 1/3rd of the full motor loop.  My reasoning is that this affects the performance of the model (and VP) so, that calculations of the full motor performance are quite inaccurate.

What is your experience? If we count the partial motor weight like 1/3 * (0.4 g - knot weight) + (knot weight), is this more accurate estimation of full motor performance than 1/3 * 0.4g?
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piecost
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« Reply #1 on: March 04, 2018, 05:23:43 PM »

Ive not flown F1D but have used partial motors. I have also wondered about this. I think that the effect is lost with the general variation due to differences in temperature and lift and sink between small and high ceiling venues. I'll also be interested to hear what others think.
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lincoln
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« Reply #2 on: March 05, 2018, 11:58:40 AM »

You could always cut off a knot and weigh it.
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adanjo
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« Reply #3 on: March 05, 2018, 12:52:46 PM »


What is your experience? If we count the partial motor weight like 1/3 * (0.4 g - knot weight) + (knot weight), is this more accurate estimation of full motor performance than 1/3 * 0.4g?

Yes.
And I consider the weight of the O ring(s), too, because I always use two rings for full motor and one ring for partial motor.

Aki
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Hepcat
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« Reply #4 on: March 05, 2018, 11:12:38 PM »

Spr.
You are right to raise the question but the way you raise it indicates that you really know what to do already.
Piecost
Is correct, of course, to mention ever present variables.
Adango
Is correct, of course, to define what is being used.

All I can do is to repeat the golden rule for success in Indoor Flying - Keep Records. If you have turns, torques, trims,times all recorded you won't care if you motor is 1/2 or 63% as long as the weights are correct!
John
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